The present invention relates to a process for preparing metal coated activated carbon supported catalysts by effecting a cation exchange with acid groups on the surface of an activated carbon support, separating the thus treated activated carbon support.
The present invention is an improvement of the process described by Furuoya, et al. for preparing palladium-on-carbon catalysts, in which the palladium is deposited as metal crystallites. Furuoya's method was described in International Chemical Engineering, volume 10, pages 333 to 338 (April 1970), the entire disclosure of which is hereby incorporated by reference. Furuoya's method provides for oxidizing an active carbon support with nitric acid; impregnating the oxidized carbon support for 48 hours with an aqueous solution containing a palladium-amine complex; isolating the palladium impregnated activated carbon support by filtration, washing and drying; and activating the palladium impregnated activated carbon support by reduction with hydrogen, oxidation in air, and a final reduction in hydrogen. The method of preparation is obviously laborious, for example, activated carbon oxidized with nitric acid is extremely difficult to filter because it forms a strongly coherent colloidal filter cake.
Another disadvantage of the Furuoya process is that the carbon support is saturated throughout with palladium-amine solution which upon drying may result in the formation of large metal crystallites which do not exhibit desirable catalytic properties.
The present invention is an improvement in the Furuoya process which permits the production of a catalyst of superior quality obtained with less difficulty in the filtration operation, and further without requiring the laborious activation treatment described above.